JPH0613015A - Ion implantation device - Google Patents

Abstract

PURPOSE:To judge whether there is malfunction by making comparison between a reference value and a state value consisting of resolution or standard deviation of a specific peak part in a mass spectrum indicating the mass distribution of an impurity ion in an ion beam. CONSTITUTION:An ion implantation device comprises a device main body part 1 having an ion source for generating an impurity ion, as well as a mass spectrograph for analyzing the impurity ion with a magnetic field, a target part 2 for holding an ion irradiation objective and for detecting a beam current, and a judgment part 3. A state value consisting of resolution or standard deviation of a specific peak part in a mass spectrum is determined by the judgment part 3, and this value is compared with a reference value in the normal condition to know the state of the peak part, and it is judged whether there is malfunction such as abnormality in each apparatus or position displacement. Correct judgment is expected without requiring experience or judgment of an operator at the time of judgment, while the burden on the operator can thus be alleviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implanter for determining the presence or absence of a defect based on a mass spectrum showing a mass distribution of impurity ions in an ion beam extracted from an ion source.

[0002]

2. Description of the Related Art In general, an ion implantation apparatus uses a mass spectrometer 52 to analyze impurity ions extracted from an ion source 51, as shown in FIG. 4, in order to implant desired impurity ions into an ion irradiation target. , Analysis slit 53
By passing through the slit hole 53a, the ion irradiation target is irradiated with the ion beam 54 made of specific impurity ions. At this time, the ion beam 54 is generated by the slit hole 5 of the analysis slit 53 when each device operates normally and is installed at a proper position.
Since it advances so as to focus on the central portion of 3a, it reaches the ion irradiation target without contacting the analysis slit 53.

However, when each device is abnormal or deviated from the proper position, the focus position of the ion beam 54 traveling from the mass analyzer 52 is the slit of the analysis slit 53, as shown in FIG. Since the ion beam 54 is displaced from the center of the hole 53a,
It reaches the ion irradiation target while being in contact with.

The analysis slit 53 is made of a material that is difficult to be sputtered even if the ion beam 54 comes into contact therewith. However, when the ion beam 54 comes into contact with the analysis slit 53 for a long time, wear due to spattering occurs. Further, about 5% of the atoms sputtered from the ion beam 54 carry electric charges (positive ions) and travel with the ion beam 54 toward the ion irradiation target. On the other hand, although about 95% of the sputtered atoms are neutral, they collide with impurity ions when they travel with the ion beam 54 to become positive cluster ions and travel toward the ion irradiation target. become. Then, with respect to these charged atoms, atoms having a small mass enter the object to be ion-irradiated and atoms having a large mass adhere to the surface, resulting in contamination and poor implantation.

Therefore, in the conventional ion implantation apparatus, the mass spectrum generated from the ion beam 54 is changed from the state shown in FIG. 6 to the state shown in FIG. 7 when a defect such as an abnormality of the equipment or a position shift occurs. Focusing on the above, the presence or absence of a defect such as a device abnormality or a positional deviation is determined by visually inspecting the state of the mass spectrum (the shape of the peak portion and the current value between the peak portions). That is, for example, as shown in FIG. 6, when the current value between the peak portions is low,
It is determined that no defect has occurred, and for example, as shown in FIG. 7, when the current value between the peak portions is high, it is determined that the defect has occurred.

[0006]

However, in the above-mentioned conventional ion implantation apparatus, since the state of the mass spectrum is visually inspected, the judgment depends on the experience and judgment of the operator, and as a result, the judgment is inaccurate. There is a problem that it is easy to become. In addition, there is a problem that the creation of the mass spectrum and the visual determination increase the burden on the operator. Therefore, conventionally, a method of determining the presence or absence of a defect from the increase or decrease of the defective rate of the ion irradiation target may be adopted, but in this case, there is a problem of reducing the yield of the ion irradiation target. It will be.

Therefore, it is an object of the present invention to provide an ion implanter capable of accurately determining the presence or absence of a defect without depending on the experience and the determination of an operator.

[0008]

In order to solve the above-mentioned problems, the ion implantation apparatus of the present invention has a problem based on a mass spectrum showing a mass distribution of impurity ions in an ion beam extracted from an ion source. The presence or absence is determined, and has the following features.

That is, the ion implanter obtains a state value consisting of the resolution or standard deviation of a specific peak portion in the mass spectrum, and compares this state value with the reference value of the peak portion to determine whether there is a defect. It is characterized by having a judging means for judging.

[0010]

According to the above construction, the determining means of the ion implanter obtains a state value consisting of the resolution or standard deviation of a specific peak portion in the mass spectrum, and compares this state value with a reference value to determine the peak value. By grasping the state of the parts, it is determined whether or not there is a defect such as an abnormality or misalignment of each device. Therefore, since this ion implantation apparatus does not require the experience and judgment of the operator when determining whether there is a defect, it is possible to accurately determine whether there is a defect and the burden on the operator is reduced. It can be done.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 2, the ion implantation apparatus according to this embodiment has an apparatus main body 1 for generating an ion beam and advancing it toward an ion irradiation target. The apparatus main body 1 has an ion source that generates impurity ions and a mass analyzer that analyzes the impurity ions extracted from the ion source by a magnetic field. This mass analyzer analyzes the magnetic flux density of the magnetic field. It can be changed arbitrarily by an electromagnet.

The above mass spectrometer analyzes an ion beam consisting of impurity ions of each mass, then advances the ion beam passing through the orbit of the central portion while converging on the exit side, and at a position at a predetermined distance from the exit side. You can focus on. And at the position of this predetermined distance,
An analysis slit having a slit hole is provided, and the slit hole allows only an ion beam consisting of specific impurity ions focused at that position to pass therethrough.

A target portion 2 for holding an ion irradiation object such as a wafer is arranged in the traveling direction of the ion beam. The target unit 2 is adapted to allow the ion irradiation target to exist in the passage of the ion beam and to detect the beam current of the ion beam. The target unit 2 is connected to the determination unit 3 (determination means) and outputs the detected beam current to the determination unit 3.

The determination unit 3 is also connected to the mass analyzer of the apparatus body 1 described above so as to output a mass value control signal to the mass analyzer, and also to detect a mass value detection signal. It is designed to be obtained from a mass spectrometer. The mass value control signal is a signal for changing the magnetic flux density by controlling the analyzing electromagnet, and the mass value detection signal is
It is a signal indicating the mass number of impurity ions of the ion beam passing through the orbit at the center of the mass spectrometer.

The determination unit 3 has a calculation unit and a storage unit, and the storage unit creates a mass spectrum based on the mass value control signal, the mass value detection signal, and the beam current. I remember my routine. The mass spectrum indicates the mass distribution of impurity ions in the ion beam extracted from the ion source based on the relationship between the beam current and the mass number of the analyzed ion beam. Further, this storage unit stores a failure determination routine consisting of a resolution determination routine or a standard deviation determination routine. By determining the value (resolution or standard deviation) and comparing this state value with the reference value that indicates the state of the peak part under normal conditions, it is possible to determine the presence or absence of malfunction such as abnormality or misalignment of each device. ing.

The operation of determining the presence or absence of a defect by executing the resolution determination routine in the above configuration will be described.

First, by executing the mass spectrum generation routine, the magnetic flux density of the mass analyzer is changed by the mass value control signal, and the analysis voltage proportional to this magnetic flux density and the beam detected at each analysis voltage are obtained. The current and the analysis voltage value V _M and the beam current value I _B are stored in the storage unit. Then, the above-mentioned analysis voltage value V _M
A mass spectrum is created based on the beam current value I _B and the beam current value I _B.

Next, from the beam current value I _B obtained by executing the mass spectrum generation routine, as shown in FIG. 1, the maximum beam current value I ₀ showing the peak value at a specific peak portion and the maximum beam current value I ₀ are obtained. The analysis voltage value V ₀ corresponding to the current value I ₀ will be determined. At this time, the measurement data composed of the beam current value I _B and the analysis voltage value V ₀ described above includes a fluctuation (measurement error). Therefore, since the maximum beam current I ₀ and the analysis voltage value V ₀ cannot be determined only by specific measurement data, the average value is obtained from a large number of measurement data to the extent that fluctuation (measurement error) does not affect the calculated value. It will be decided after conversion processing.

[0020] That is, if the beam current value I _B and analyzes the voltage value V _M is n sets up 0 to n, the measured beam current value I _B is the beam current value I _k to k-th, analytical voltage value V _M will be the analysis voltage value V _k . However, V
_k ≦ V _{k + 1} . Then, the average value I _l of the beam current value I _k is obtained for the m total of 2m + 1 pieces of measurement data in which “k” is before and after the 1 (el) th.

[0021]

[Equation 1]

After that, "l (el)" is moved from m to nm, and the maximum average value I _l is set as the maximum beam current value I _0, and the l (el) th analysis voltage value V at that time is set. When the _k and analyzed voltage value V _0, the maximum beam current value I ₀ 1 /
2 half I _0/2 analysis voltage value V ₁ corresponding to the value is that is determined as follows.

That is, first, the measurement data satisfying the following conditions is extracted from the measurement data of the beam current value I _k and the analysis voltage value V _k .

V _k <V ₀ 0.4I ₀ ≤I _k ≤0.6I ₀ Then, if the extracted measurement data are p sets of 1 to p, the analysis voltage value V ₁ is obtained by the following equation. Will be done.

[0025]

[Equation 2]

[0026] In _{addition, V 0 <V k, 0.4I} 0 ≦ I k ≦ 0.6
Regarding the measurement data satisfying the condition of I ₀ , if the extracted measurement data are q sets of 1 to q, the analysis voltage value V ₂ is obtained by the following equation.

[0027]

[Equation 3]

Then, the resolution M / ΔM is obtained by the following equation based on the above both analysis voltage values V ₁ and V ₂ .

[0029]

[Equation 4]

After this, the resolution M calculated by the above equation
/ ΔM (state value) will be compared with the previously stored reference resolution (reference value), and if the resolution M / ΔM is a value larger than the reference resolution, the device has a malfunction. It will be determined that there is no. On the other hand, when the resolution M / ΔM is a value smaller than the reference resolution, it is considered that a malfunction has occurred in the device and, for example, an alarm or the like is issued, or the injection operation is stopped.

The analysis voltage value V ₀ · V used in the above equation
It is desirable that ₁ · V ₂ is measured with a significant figure of 6 digits or more. That is, the analysis voltage values V ₀ · V ₁ · V ₂ are
Usually, it is designed to be measured with a significant figure of 3 or 4 digits. For example, analysis voltage value V ₀ = 4.00V, analysis voltage value V ₁ = 3.99V, analysis voltage value V ₂ = 4. Assuming that a measured value of 01 V is obtained, the resolution M / ΔM is V ₀ /
_{2 (V 2 -V 1) =} 4.00 / 2 (4.01-3.99) = 1
It becomes 00.

[0032] In this case, the value of _{(V 2 -V 1) "0.02} "
May vary from 0.01 to 0.03, so the resolution M / ΔM is 4.00 / 0.02 to 4.00 / 0.06 (2
It can be judged that it seems to be in the range from 00 to 67). However, in this range of resolution M / ΔM, a difference of several% cannot be detected.

Therefore, the analysis voltage values V ₀ · V ₁ · V ₂ are set to 6
Measurement is performed using significant figures of digits, for example, analysis voltage value V ₀ =
4.00000V, analytical voltage value V ₁ = 3.98633V, the measured value of the analysis voltage value V ₂ = 4.01367V is to obtain resolution M / .DELTA.M _{is, V 0/2 (V 2} -V 1) = Four.
00000/2 (4.01367-3.98633) = 73.
It becomes 153. And in this case, (V ₂ −V ₁ )
Since the value of “0.02734” may vary from 0.02733 to 0.03275, the resolution M / ΔM is 4.00.
000 / 0.05466 to 4.00000 / 0.05470
The range is (73.180 to 73.125). Therefore, according to this range of resolution M / ΔM, it is possible to detect a difference of several percent.

Next, the operation of determining the presence / absence of a defect by executing the standard deviation determination routine will be described.

In this standard deviation determination routine, as shown in FIG. 3, the shape of the mass spectrum is approximated by using the normal distribution function of the following equation, and the shape of a specific peak portion of the mass spectrum is determined by the value of standard deviation σ. By using the information, it is possible to determine whether or not there is a malfunction in the device.

[0036]

[Equation 5]

That is, there are n values of x from 1 to n, and x
The standard deviation when the distribution of the value of is a normal distribution is obtained by the following formula.

[0038]

[Equation 6]

The above x gives y = f (x),
When f (x) indicates a normal distribution function, x _k in the above equation is y _k
It can be treated as a distribution when it appears once. Therefore, the standard deviation when x _k has a uniform distribution is obtained by the following equation.

[0040]

[Equation 7]

Then, using the above equation and the beam current value I _k and the analysis voltage value V _k , the average value V ₀ and the standard deviation σ are obtained as in the following equation.

[0042]

[Equation 8]

After that, the standard deviation σ (state value) calculated by the above equation is compared with the reference standard deviation (reference value) stored in advance, and the standard deviation σ is higher than the reference standard deviation. If the value is small, it is determined that the device is not defective. On the other hand, standard deviation σ
Is larger than the standard standard deviation, it means that a malfunction has occurred in the device and, for example, an alarm is issued.

As described above, in the ion implantation apparatus according to the present embodiment, the determination unit 3 executes the defect determination routine including the resolution determination routine or the standard deviation determination routine, so that the resolution or standard of a specific peak portion in the mass spectrum is determined. The state value, which is the deviation, is obtained, and the state of the peak portion of the mass spectrum is grasped by comparing this state value with a reference value, and it is determined whether or not there is a malfunction such as an abnormality or misalignment of each device. . Therefore, since this ion implantation apparatus does not require the experience and judgment of the operator when determining whether there is a defect, it is possible to accurately determine whether there is a defect and the burden on the operator is reduced. It can be done.

[0045]

As described above, the ion implantation apparatus of the present invention is capable of determining the presence / absence of a defect based on the mass spectrum showing the mass distribution of impurity ions in the ion beam extracted from the ion source. There is a determination means for determining the presence or absence of a defect by obtaining a state value consisting of the resolution or standard deviation of a specific peak portion in the mass spectrum, and comparing this state value with the reference value of the peak portion. It has a structure.

Thus, the determining means compares the state value of the specific peak portion in the mass spectrum with the reference value to grasp the state of the peak portion, and determines whether or not there is a malfunction such as an abnormality or misalignment of each device. This eliminates the need for the operator's experience and judgment when determining the presence / absence of a defect, and as a result, the presence / absence of a defect can be accurately determined and the burden on the operator can be reduced. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a peak portion in a mass spectrum of the present invention.

FIG. 2 is a block diagram of an ion implanter.

FIG. 3 is an explanatory diagram showing a normal distribution.

FIG. 4 shows a conventional example and is an explanatory view showing a traveling direction of an ion beam in a normal state.

FIG. 5 is an explanatory diagram showing a traveling direction of an ion beam at the time of abnormality.

FIG. 6 is an explanatory diagram showing a state of a mass spectrum in a normal state.

FIG. 7 is an explanatory diagram showing a state of a mass spectrum at the time of abnormality.

[Explanation of symbols]

 1 Device main body 2 Target part 3 Judgment part (judgment means)

Claims (1)

[Claims] 1. An ion implanter for determining the presence or absence of a defect on the basis of a mass spectrum showing the mass distribution of impurity ions in an ion beam extracted from an ion source. An ion implantation apparatus comprising: a determining unit that determines a presence or absence of a defect by obtaining a state value composed of resolution or standard deviation and comparing the state value with a reference value of the peak portion.